I've never really found much practical use for them. I used them today. I had to make a slight adjustment to the satellite dish to peak up the signal. My wife stayed inside and monitored the signal level on the screen and read the numbers out to me. I managed to get it from 82% up to 97%. 80% seems to be the threshold, below which the picture starts to break up.
I've used them for that purpose a few times, but that's about all I've ever done.
![Image](http://london.marknmel.com/albums/Radio/IMG_1040.sized.jpg)